Thunberg made headlines worldwide previous year when a spate of unseasonal forest fires convinced her to protest outside of Sweden's parliament building.
George Bond, a student protester in London who travelled several hours to demonstrate outside the British Parliament, told Al Jazeera it was "imperative that young people are able to break the cycle of inaction that directly threatens the security of their future on this planet".
One of the city's Labour MPs, Lloyd Russell-Moyle, joined the march saying "students will learn more today than they will in the classroom".
The Green New Deal is a wide-reaching initiative that its supporters say aims to transform the economy to combat the issues of climate change and inequality. We understand that you view this plan as sufficient for Hong Kong, however, for the safeguarding of our futures, we believe Hong Kong has the potential to do more.
That conversation is likely to get louder, with several US presidential hopefuls planning to campaign on climate change.
The students came from a number of schools across the city with one common goal, demanding the Government declare a "climate emergency" and allow young people to have their say on their environmental future.
They said they did not want to strike, play truant or waste the time of their teachers but they had to make a stand. If we can get the government to place sanctions on Carbon dioxide emissions, then we can really slow down the progression of climate change.
16-Year-Old Climate Activist Greta Thunberg Nominated For Nobel Peace Prize
"We're protesting again because the reaction last time was not what we were looking for".
After her speeches at the United Nations climate change conference in Poland and at the Davos forum, she became an example for many young people all over the world, who since have promoted similar initiatives.
A group of year 12 students from Nelson College for Girls said their parents and their principal supported their choice to "strike" from school.
"We just need to be telling youth to speak up and get educated about this, because their voice can really influence policy", said CU Boulder freshman Emilie Craig.
Supporting the kids: The 62-year-old wrote on Instagram: "You know the world has changed coz (sic) we caught a train to join #ClimateStrike with the school kids, they were amazing".
The campaign, started by 16-year-old Swedish activist Greta Thunberg, saw its first global protest in February.
Today's protest, which will be mirrored by young activists around the world, is slated to be even bigger.
She says striking school is extreme, and there's a reason for that. We have the solution and the facts and the data and the science. "The oceans are rising, so are we", read another in Sydney.